Transactional operations in multi-master distributed data management systems

ABSTRACT

One embodiment provides for a method for grooming transactional operations in a multi-master distributed data management system including maintaining transactional operations in at least one transaction-local side-log. A table log scan is performed for a table including recording identification for each record in a log. Each column in the table is loaded with column values based on the identifications. Records based on the column values are written to the groomed transaction blocks that are table based, and the tuple sequence numbers for each record on groomed blocks are generated. The table is shared/sharded across nodes handling transactional operations in the multi-master distributed data management system to increase processing handling of the transactional operations.

BACKGROUND

Conventional data management systems that target high-availability have to allow transactional operations, such as updates, deletes, and inserts (UDIs) to go to any replica of data. The transactional operations also target compatibility with the big data ecosystem, which uses append-only (and hence mutation unfriendly) storage streams because of their superiority in efficient read and write operations and space consumption.

SUMMARY

Embodiments relate to transactional operations in multi-master distributed data management systems. One embodiment provides for a method for grooming transactional operations in a multi-master distributed data management system including maintaining transactional operations in at least one transaction-local side-log. A table log scan is performed for a table including recording identification for each record in a log. Each column in the table is loaded with column values based on the identifications. Records based on the column values are written to the groomed transaction blocks that are table based, and the tuple sequence numbers for each record on groomed blocks are generated. The table is shared/sharded across nodes handling transactional operations in the system to increase processing handling of the transactional operations.

These and other features, aspects and advantages of the present invention will become understood with reference to the following description, appended claims and accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a cloud computing environment, according to an embodiment;

FIG. 2 depicts a set of abstraction model layers, according to an embodiment;

FIG. 3 is a network architecture for a multi-master distributed data management system, according to an embodiment;

FIG. 4 shows a representative hardware environment that may be associated with the servers and/or clients of FIG. 1, according to an embodiment;

FIG. 5 is a block diagram illustrating a multi-master distributed data management system for performing a grooming process for transactional operations, according to one embodiment;

FIG. 6 illustrates an example architecture for performing a grooming process in a multi-master distributed data management system, according to one embodiment;

FIG. 7 illustrates a life cycle example for data in a multi-master distributed data management system, according to one embodiment;

FIG. 8 illustrates an example of grooming data in a multi-master distributed data management system, according to one embodiment;

FIG. 9 illustrates an example block diagram for a grooming evaluation process, according to one embodiment;

FIG. 10 illustrates an example write process for the grooming evaluation process of FIG. 9, according to one embodiment; and

FIG. 11 illustrates a block diagram for a process for grooming transactional operations in a multi-master distributed data management system, according to one embodiment.

DETAILED DESCRIPTION

The descriptions of the various embodiments have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

It is understood in advance that although this disclosure includes a detailed description of cloud computing, implementation of the teachings recited herein are not limited to a cloud computing environment. Rather, embodiments of the present invention are capable of being implemented in conjunction with any other type of computing environment now known or later developed.

Embodiments relate to transactional operations (e.g., updates, deletes, inserts, etc.) in multi-master distributed data management systems. One embodiment provides a method for grooming transactional operations in a multi-master distributed data management system including maintaining transactional operations in at least one transaction-local side-log. A table log scan is performed for a table including recording identification for each record in a log. Each column in the table is loaded with column values based on the identifications. Records/tuples based on the column values are written to the groomed transaction blocks that are table based, and the tuple sequence numbers (TSNs) for each record on groomed blocks are generated. The table is shared/sharded across nodes handling transactional operations in the system to increase processing handling of the transactional operations.

Cloud computing is a model of service delivery for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, network bandwidth, servers, processing, memory, storage, applications, virtual machines (VMs), and services) that can be rapidly provisioned and released with minimal management effort or interaction with a provider of the service. This cloud model may include at least five characteristics, at least three service models, and at least four deployment models.

Characteristics are as follows:

On-demand self-service: a cloud consumer can unilaterally provision computing capabilities, such as server time and network storage, as needed and automatically, without requiring human interaction with the service's provider.

Broad network access: capabilities are available over a network and accessed through standard mechanisms that promote use by heterogeneous, thin or thick client platforms (e.g., mobile phones, laptops, and PDAs).

Resource pooling: the provider's computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to demand. There is a sense of location independence in that the consumer generally has no control or knowledge over the exact location of the provided resources but may be able to specify location at a higher level of abstraction (e.g., country, state, or data center).

Rapid elasticity: capabilities can be rapidly and elastically provisioned and, in some cases, automatically, to quickly scale out and rapidly released to quickly scale in. To the consumer, the capabilities available for provisioning often appear to be unlimited and can be purchased in any quantity at any time.

Measured service: cloud systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active consumer accounts). Resource usage can be monitored, controlled, and reported, thereby providing transparency for both the provider and consumer of the utilized service.

Service Models are as follows:

Software as a Service (SaaS): the capability provided to the consumer is the ability to use the provider's applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface, such as a web browser (e.g., web-based email). The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited consumer-specific application configuration settings.

Platform as a Service (PaaS): the capability provided to the consumer is the ability to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages and tools supported by the provider. The consumer does not manage or control the underlying cloud infrastructure including networks, servers, operating systems, or storage, but has control over the deployed applications and possibly application-hosting environment configurations.

Infrastructure as a Service (IaaS): the capability provided to the consumer is the ability to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, deployed applications, and possibly limited control of select networking components (e.g., host firewalls).

Deployment Models are as follows:

Private cloud: the cloud infrastructure is operated solely for an organization. It may be managed by the organization or a third party and may exist on-premises or off-premises.

Community cloud: the cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, and compliance considerations). It may be managed by the organizations or a third party and may exist on-premises or off-premises.

Public cloud: the cloud infrastructure is made available to the general public or a large industry group and is owned by an organization selling cloud services.

Hybrid cloud: the cloud infrastructure is a composition of two or more clouds (private, community, or public) that remain unique entities but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds).

A cloud computing environment is a service oriented with a focus on statelessness, low coupling, modularity, and semantic interoperability. At the heart of cloud computing is an infrastructure comprising a network of interconnected nodes.

Referring now to FIG. 1, an illustrative cloud computing environment 50 is depicted. As shown, cloud computing environment 50 comprises one or more cloud computing nodes 10 with which local computing devices used by cloud consumers, such as, for example, personal digital assistant (PDA) or cellular telephone 54A, desktop computer 54B, laptop computer 54C, and/or automobile computer system 54N may communicate. Nodes 10 may communicate with one another. They may be grouped (not shown) physically or virtually, in one or more networks, such as private, community, public, or hybrid clouds as described hereinabove, or a combination thereof. This allows the cloud computing environment 50 to offer infrastructure, platforms, and/or software as services for which a cloud consumer does not need to maintain resources on a local computing device. It is understood that the types of computing devices 54A-N shown in FIG. 2 are intended to be illustrative only and that computing nodes 10 and cloud computing environment 50 can communicate with any type of computerized device over any type of network and/or network addressable connection (e.g., using a web browser).

Referring now to FIG. 2, a set of functional abstraction layers provided by the cloud computing environment 50 (FIG. 1) is shown. It should be understood in advance that the components, layers, and functions shown in FIG. 2 are intended to be illustrative only and embodiments of the invention are not limited thereto. As depicted, the following layers and corresponding functions are provided:

Hardware and software layer 60 includes hardware and software components. Examples of hardware components include: mainframes 61; RISC (Reduced Instruction Set Computer) architecture based servers 62; servers 63; blade servers 64; storage devices 65; and networks and networking components 66. In some embodiments, software components include network application server software 67 and database software 68.

Virtualization layer 70 provides an abstraction layer from which the following examples of virtual entities may be provided: virtual servers 71; virtual storage 72; virtual networks 73, including virtual private networks; virtual applications and operating systems 74; and virtual clients 75.

In one example, a management layer 80 may provide the functions described below. Resource provisioning 81 provides dynamic procurement of computing resources and other resources that are utilized to perform tasks within the cloud computing environment. Metering and pricing 82 provide cost tracking as resources are utilized within the cloud computing environment and billing or invoicing for consumption of these resources. In one example, these resources may comprise application software licenses. Security provides identity verification for cloud consumers and tasks as well as protection for data and other resources. User portal 83 provides access to the cloud computing environment for consumers and system administrators. Service level management 84 provides cloud computing resource allocation and management such that required service levels are met. Service Level Agreement (SLA) planning and fulfillment 85 provide pre-arrangement for, and procurement of, cloud computing resources for which a future requirement is anticipated in accordance with an SLA.

Workloads layer 90 provides examples of functionality for which the cloud computing environment may be utilized. Examples of workloads and functions which may be provided from this layer include: mapping and navigation 91; software development and lifecycle management 92; virtual classroom education delivery 93; data analytics processing 94; transaction processing 95; and grooming transactional operations in a multi-master distributed data management system processing 96. As mentioned above, all of the foregoing examples described with respect to FIG. 2 are illustrative only, and the invention is not limited to these examples.

It is understood all functions of one or more embodiments as described herein may be typically performed by the processing system 300 (FIG. 3) or the cloud environment 410 (FIG. 4), which can be tangibly embodied as hardware processors and with modules of program code. However, this need not be the case for non-real-time processing. Rather, for non-real-time processing the functionality recited herein could be carried out/implemented and/or enabled by any of the layers 60, 70, 80 and 90 shown in FIG. 2.

It is reiterated that although this disclosure includes a detailed description on cloud computing, implementation of the teachings recited herein are not limited to a cloud computing environment. Rather, the embodiments of the present invention may be implemented with any type of clustered computing environment now known or later developed.

FIG. 3 illustrates a network architecture 300, in accordance with one embodiment. As shown in FIG. 3, a plurality of remote networks 302 are provided, including a first remote network 304 and a second remote network 306. A gateway 301 may be coupled between the remote networks 302 and a proximate network 308. In the context of the present network architecture 300, the networks 304, 306 may each take any form including, but not limited to, a LAN, a WAN, such as the Internet, public switched telephone network (PSTN), internal telephone network, etc.

In use, the gateway 301 serves as an entrance point from the remote networks 302 to the proximate network 308. As such, the gateway 301 may function as a router, which is capable of directing a given packet of data that arrives at the gateway 301, and a switch, which furnishes the actual path in and out of the gateway 301 for a given packet.

Further included is at least one data server 314 coupled to the proximate network 308, which is accessible from the remote networks 302 via the gateway 301. It should be noted that the data server(s) 314 may include any type of computing device/groupware. Coupled to each data server 314 is a plurality of user devices 316. Such user devices 316 may include a desktop computer, laptop computer, handheld computer, printer, and/or any other type of logic-containing device. It should be noted that a user device 311 may also be directly coupled to any of the networks in some embodiments.

A peripheral 320 or series of peripherals 320, e.g., facsimile machines, printers, scanners, hard disk drives, networked and/or local storage units or systems, etc., may be coupled to one or more of the networks 304, 306, 308. It should be noted that databases and/or additional components may be utilized with, or integrated into, any type of network element coupled to the networks 304, 306, 308. In the context of the present description, a network element may refer to any component of a network.

According to some approaches, methods and systems described herein may be implemented with and/or on virtual systems and/or systems, which emulate one or more other systems, such as a UNIX system that emulates an IBM z/OS environment, a UNIX system that virtually hosts a MICROSOFT WINDOWS environment, a MICROSOFT WINDOWS system that emulates an IBM z/OS environment, etc. This virtualization and/or emulation may be implemented through the use of VMWARE software in some embodiments.

FIG. 4 shows a representative hardware system 400 environment associated with a user device 316 and/or server 314 of FIG. 3, in accordance with one embodiment. In one example, a hardware configuration includes a workstation having a central processing unit 410, such as a microprocessor, and a number of other units interconnected via a system bus 412. The workstation shown in FIG. 4 may include a Random Access Memory (RAM) 414, Read Only Memory (ROM) 416, an I/O adapter 418 for connecting peripheral devices, such as disk storage units 420 to the bus 412, a user interface adapter 422 for connecting a keyboard 424, a mouse 426, a speaker 428, a microphone 432, and/or other user interface devices, such as a touch screen, a digital camera (not shown), etc., to the bus 412, communication adapter 434 for connecting the workstation to a communication network 435 (e.g., a data processing network) and a display adapter 436 for connecting the bus 412 to a display device 438.

In one example, the workstation may have resident thereon an operating system, such as the MICROSOFT WINDOWS Operating System (OS), a MAC OS, a UNIX OS, etc. In one embodiment, the system 400 employs a POSIX® based file system. It will be appreciated that other examples may also be implemented on platforms and operating systems other than those mentioned. Such other examples may include operating systems written using JAVA, XML, C, and/or C++ language, or other programming languages, along with an object oriented programming methodology. Object oriented programming (OOP), which has become increasingly used to develop complex applications, may also be used.

FIG. 5 is a block diagram illustrating a system 500 that may be employed for grooming transactional operations, according to one embodiment. In one embodiment, the system 500 includes client devices 510 (e.g., mobile devices, smart devices, computing systems, etc.), a cloud or resource sharing environment 520 (e.g., a public cloud computing environment, a private cloud computing environment, a datacenter, etc.), and servers 530. In one embodiment, the client devices are provided with cloud services from the servers 530 through the cloud or resource sharing environment 520.

In one embodiment, system 500, a periodic background process referred to as grooming, analyzes transactional operations (e.g., updates, deletes, inserts (UDIs)) from multi-statement transactions executed on a multi-master system, and publishes the UDIs on an append-only storage stream in a way that allows monotonic transactional consistent reads of that data. In one embodiment, for the grooming process the multi-master system maintains/keeps the UDIs of ongoing multi-statement transactions in a transaction-local side-log. Only upon a successful transaction commit, the transaction-local side-logs are appended to the log stream. The grooming process only reads the log stream, therefore, the grooming process avoids being aware of uncommitted transaction changes. The thread performing the grooming process (also referred to as “groomer”) provides a cursor or indication on the log stream to remember where it left off in the previous grooming cycle. The log stream that is prior to where the groomer's cursor or indication points to is marked for deletion. In one embodiment, a process referred to as a pruning process, deletes this portion of the log stream if no ongoing read operation is on that stream. Both the groomer and the read operations following the previous groom cycle, therefore, start reading the not yet groomed log stream. This further ensures the monotonic reads of the data. Additionally, the grooming process only reads log streams with timestamps (e.g., commit time for that log item) that are earlier than the start time of the grooming process, which ensures bounded execution time for a grooming cycle.

FIG. 6 illustrates an example architecture 600 for performing a grooming process in a multi-master distributed data management system, according to one embodiment. In one embodiment, the architecture 600 includes applications 610, task coordinators 620, execution engines 630, for analytical nodes 650, execution engines 640 for transactional nodes 655 and storage 660. In one embodiment, the applications 610 may include analytics applications 611 that tolerate slightly stale data and requires most recent data, and high volume transaction applications 612. In one embodiment, the analytical nodes 650 only handle read-only operations. The transactional nodes 655 are responsible for grooming transaction operations (e.g., UDIs). The execution engines 640 include multiple execution engines 645 connected with memory devices 646 (e.g., solid state drive(s) (SSD) and non-volatile memory (NVM), such as read-only memory, flash memory, ferroelectric RAM, magnetic computer storage devices (e.g., hard disk drives, floppy disks, and magnetic tape, optical discs, etc.). The storage 660 may include a shared file system, object store, or both.

In one embodiment, to speed up UDI operations through parallelism, the tables in the multi-master system that includes the architecture 600 are sharded or partitioned across nodes handling transactions based upon a subset of a primary (single-column or composite) key. A table shard is also assigned to (a configurable number of) multiple nodes (transactional nodes 655) for higher availability. In addition to the transactional nodes 655 that are responsible from UDI operations and lookups on data, the analytical nodes 650 are only responsible for analytical read requests. A distributed coordination system includes the task coordinators 620 that manage the meta-information related to sharding and replication, and a catalog maintains the schema information for each table. One or more embodiments also allow external readers to read data ingested via the multi-master system without involving the local system components, but those readers will be unable to see the latest transactional data stored on the transactional nodes 655 handling UDI operations.

In one embodiment, each transaction handled by the architecture 600 maintains its un-committed changes in a transaction-local side-log 811 (FIG. 8) composed of one or more log blocks. Each log block may contain transactions for only one table. At commit time, the transaction appends its transaction-local side-log 811 to the log 812 (FIG. 8), which is kept both in storage 660 (memory 810, FIG. 8) and persisted on disk (SSD/NVM 646 (830 (FIG. 8)). Additionally, the transaction-local side-log 811 is copied to each of the other transactional nodes 655 that are responsible for maintaining a replica of that shard's data, for availability. While any replica of a shard may process any transactional request for that shard (multi-master), one of the replicas periodically invokes a grooming operation or process. This grooming operation scans the log 812 and groups together the log blocks from multiple (committed) transactions for the same table, creating larger groomed blocks containing data only from a single table (see, e.g., FIG. 8, groomed data 855). In addition to merging log blocks, the grooming operation may also perform conflict resolution 930 (FIG. 9) for data items. The groomed data blocks 850 are then flushed to an append-only storage stream, which is also a shared distributed file system so that other nodes can also access them. After a grooming pass, the groomer prunes the log records it has successfully groomed so that it will not occupy resources any longer, and the next pass of grooming can start from where it left off.

FIG. 7 illustrates a life cycle example 700 for data in a multi-master distributed data management system including architecture 600 (FIG. 6), according to one embodiment. In one embodiment, the life of data is represented by recent data 701 and old data 702. The recent data 701 belongs to the live zone (latest) 710 whereas the old data belongs to the groomed zone 711 (e.g., ˜1 second stale). The transactional nodes 655 belong to the live zone 710, and receive inserts, updates and delete transactional operations 720 and read-only operations 721 that need the latest data. The analytical nodes 650 belong to the groomed zone 711 and receive input 730 including: point lookups 731, business intelligent operations 732, and machine learning (read-only) operations 733. As illustrated, the data in the live zone 710 moves over to the groomed zone 711 as it becomes older data.

FIG. 8 illustrates an example 800 of grooming data in a multi-master distributed data management system, according to one embodiment. As illustrated, the un-committed changes are recorded/stored in a transaction-local side-log 811 composed of one or more log blocks. The log record 815 of a table includes the log blocks for the log (persistent) 812. The transaction appends its transaction-local side-log 811 to the log 812, which is kept both in memory 810 and persisted on disk SSD/NVM 830. In the SSD/NVM 830, the log 812 is processed in records 835 and cached as cached data 840. The groomed data 855 that results from the grooming process is stored in the shared file system 850 (or storage 660, FIG. 6).

FIG. 9 illustrates an example block diagram 900 for a grooming evaluation process, according to one embodiment. In the high-level example block diagram 900, the process includes performing a table log scan 910 for a table including recording identification (IDs) for each record in the log. The input to the table log scan 910 includes table name, and log end timestamp (for a bounded scan). The output of the table log scan 910 includes bounded TSNs (BTSNs)(i.e., the record IDs for each record in the log). In block 920, a load column process is performed. The load column takes as input the BSTNs from block 910, and outputs column values. In one embodiment, optional conflict resolution is performed in block 930 (e.g., data conflicts, etc.). In block 940, a write table process is performed. The write table process takes the column values as input, and outputs TSNs (record IDs on groomed blocks). The write table processing is further described below with reference to FIG. 10. In one embodiment, the optional processing for write/update index is performed for each index of the table. In one embodiment, the input for block 950 are index columns and TSNs, and the output are hash values.

FIG. 10 illustrates an example write table process for block 940 for the grooming evaluation process 900 of FIG. 9, according to one embodiment. In block 1010, the write table process obtains or receives a next input stride/batch/group of records from scanning the table log. In block 1020, the write table process generates unique commit timestamps. In block 1030, the write table process appends columns of the records to an in-memory buffer and generates the TSNs for the groomed transaction blocks. In block 1040, it is determined if more inputs exist and if the buffer is not full. In the case of more inputs existing and the buffer not being full, the write table process proceeds back to block 1010. Otherwise the write table process proceeds to block 1050 and flushes the in-memory buffer to the shared file system, an object store or a local cache. In block 1060 it is determined whether more input is available or not. If more input is available, the write table process proceeds back to block 1010. Otherwise, the write table process proceeds to block 1070 where the write table process notifies a distributed coordinator of a groom end point information (i.e., the log end point and last groomed block ID). In block 1080, the write table process moves a log head beyond the groom end point and prunes the log when no read processes remain.

FIG. 11 illustrates a block diagram for process 1100 for grooming transactional operations in a multi-master distributed data management system, according to one embodiment. In one embodiment, in block 1110 process 1100 maintains transactional operations in at least one transaction-local side-log. In block 1120 a table log scan is performed for a table including recording identification for each record in a log. In block 1130 each column in the table is loaded with column values based on the identifications. In block 1140 TSNs are generated for the records, and the records on groomed transaction blocks are written to the table based on the column values. The table is shared/sharded across nodes handling transactional operations in the multi-master distributed data management system to increase processing handling of the transactional operations.

In one embodiment, block 1140 may further include receiving a next input group of records from scanning the table, generating unique commit timestamps, appending columns of the records to an in-memory buffer and generating the TSNs for the records written to the groomed transaction blocks. Upon a determination that there is no additional input group of records and the in-memory buffer is not full, block 1140 further includes flushing the in-memory buffer to at least one of a shared file system, an object store or a local cache. Otherwise, the process 1100 proceeds back to receive the next input group of records from scanning the table.

In one embodiment, process 1100 may further include if a further input group of records is not available, notifying a distributed coordinator of a groom end point information, moving a log head beyond the groom end point and pruning the log until no read processes remain.

In one embodiment, for process 1100 the transactional operations comprise update, delete and insert operations. Upon a successful transaction commit, the transaction-local side-log is appended to a log stream. The grooming process only reads the log and avoids uncommitted transaction changes. A thread performing the grooming process maintains a cursor on the log as an indication of a previous grooming cycle.

In one embodiment, for process 1100 in the log stream, a point prior to a location that the cursor points to is marked for deletion. A pruning process deletes a portion of the log stream upon a determination that no ongoing read operation is in the portion log stream. Both the grooming process and read operations follow the previous grooming cycle such that read operations of data are monotonic. The grooming process only reads log streams with commit timestamps less than a start time of the grooming process such that a grooming cycle has a bounded execution time.

In one embodiment, process 1100 may provide that updated records are flagged with an end timestamp after the grooming process by a periodic background process such that the updated records are ignored by reading processes that need latest data or by reading processes that read data from a specific time period.

In one embodiment, process 1100 may include that the multi-master distributed data management system operates on two tiers of storage including: a first storage tier that is local to a node, and a second storage tier including a distributed shared file system or an object store. The first storage tier maintains a persistent version of the log to be used during recovery by the grooming process to start grooming from where the grooming process left off in a previous cycle, and caches frequently accessed portions of the second storage tier to enable fast access to data. The second storage tier maintains the data stream and makes the data stream available to all of nodes in the multi-master distributed data management system.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Aspects of the present invention are described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.

References in the claims to an element in the singular is not intended to mean “one and only” unless explicitly so stated, but rather “one or more.” All structural and functional equivalents to the elements of the above-described exemplary embodiment that are currently known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the present claims. No claim element herein is to be construed under the provisions of 35 U.S.C. section 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or “step for.”

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. 

What is claimed is:
 1. A method for grooming transactional operations in a multi-master distributed data management system, comprising: maintaining transactional operations in at least one transaction-local side-log; performing a table log scan for a table including recording identification for each record in a log; loading each column in the table with column values based on the identifications; and generating tuple sequence numbers for the records and writing the records on groomed transaction blocks to the table based on the column values, wherein the table is sharded across nodes handling transactional operations in the multi-master distributed data management system to increase processing handling of the transactional operations.
 2. The method of claim 1, wherein the writing further comprises: receiving a next input group of records from scanning the table; generating unique commit timestamps; appending columns of the records to an in-memory buffer; and generating the tuple sequence numbers for the records written to the groomed transaction blocks.
 3. The method of claim 2, wherein upon a determination that there is no additional input group of records and the in-memory buffer is not full, flushing the in-memory buffer to at least one of a shared file system, an object store or a local cache.
 4. The method of claim 3, further comprising: if a further input group of records is not available, notifying a distributed coordinator of a groom end point information; moving a log head beyond the groom end point; and pruning the log until no read processes remain.
 5. The method of claim 1, wherein: the transactional operations comprise update, delete and insert operations; upon a successful transaction commit, the transaction-local side-log is appended to a stream of the log; a grooming process only reads the log and avoids uncommitted transaction changes; and a thread performing the grooming process maintains a cursor on the log as an indication of a previous grooming cycle.
 6. The method of claim 5, wherein: in the log stream prior to a location that the cursor points to is marked for deletion; a pruning process deletes a portion of the log stream upon a determination that no ongoing read operation is in the portion log stream; and both the grooming process and read operations follow the previous grooming cycle such that read operations of data are monotonic.
 7. The method of claim 6, wherein: the grooming process only reads log streams with commit timestamps less than a start time of the grooming process such that a grooming cycle has a bounded execution time.
 8. The method of claim 7, wherein: updated records are flagged with an end timestamp after the grooming process by a periodic background process such that the updated records are ignored by reading processes that need latest data or by reading processes that read data from a specific time period.
 9. The method of claim 7, wherein: the multi-master distributed data management system operates on two tiers of storage comprising: a first storage tier that is local to a node, and a second storage tier including a distributed shared file system or an object store; the first storage tier maintains a persistent version of logs to be used during recovery by the grooming process to start grooming from where the grooming process left off in a previous cycle, and caches frequently accessed portions of the second storage tier to enable fast access to data; and the second storage tier maintains the data stream and makes the data stream available to all of nodes in the multi-master distributed data management system.
 10. A computer program product for grooming transactional operations in a multi-master distributed data management system, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to: maintain, by the processor, transactional operations in at least one transaction-local side-log; perform, by the processor, a table log scan for a table including recording identification for each record in a log; load, by the processor, each column in the table with column values based on the identifications; and generate and write, by the processor, tuple sequence numbers for the records and the records on groomed transaction blocks to the table based on the column values, respectively, wherein the table is sharded across nodes handling transactional operations in the multi-master distributed data management system to increase processing handling of the transactional operations.
 11. The computer program product of claim 10, wherein the write further comprises program instructions executable by the processor to cause the processor to: receive, by the processor, a next input group of records from scanning the table; generate, by the processor, unique commit timestamps; append, by the processor, columns of the records to an in-memory buffer; and generate, by the processor, the tuple sequence numbers for the records written to the groomed transaction blocks.
 12. The computer program product of claim 11, wherein upon a determination that there is no additional input group of records and the in-memory buffer is not full, flushing the in-memory buffer to at least one of a shared file system, an object store or a local cache.
 13. The computer program product of claim 12, the write further comprises program instructions executable by the processor to cause the processor to: if a further input group of records is not available, notify, by the processor, a distributed coordinator of a groom end point information; move, by the processor, a log head beyond the groom end point; and prune, by the processor, the log until no read processes remain.
 14. The computer program product of claim 10, wherein: the transactional operations comprise update, delete and insert operations; upon a successful transaction commit, the transaction-local side-log is appended to a log stream; a grooming process only reads the log and avoids uncommitted transaction changes; a thread performing the grooming process maintains a cursor on the log as an indication of a previous grooming cycle; in the log stream prior to a location that the cursor points to is marked for deletion; a pruning process deletes a portion of the log stream upon a determination that no ongoing read operation is in the portion log stream; and both the grooming process and read operations follow the previous grooming cycle such that read operations of data are monotonic.
 15. The computer program product of claim 14, wherein: the grooming process only reads log streams with commit timestamps less than a start time of the grooming process such that a grooming cycle has a bounded execution time; updated records are flagged with an end timestamp after the grooming process by a periodic background process such that the updated records are ignored by reading processes that need latest data or by reading processes that read data from a specific time period; the multi-master distributed data management system operates on two tiers of storage comprising: a first storage tier that is local to a node, and a second storage tier including a distributed shared file system or an object store; the first storage tier maintains a persistent version of logs to be used during recovery by the grooming process to start grooming from where the grooming process left off in a previous cycle, and caches frequently accessed portions of the second storage tier to enable fast access to data; and the second storage tier maintains the data stream and makes the data stream available to all of nodes in the multi-master distributed data management system.
 16. An apparatus comprising: a memory configured to store instructions; and a processor configured to execute the instructions to: maintain transactional operations in at least one transaction-local side-log, perform a table log scan for a table including recording identification for each record in a log, load each column in the table with column values based on the identifications, and generate tuple sequence numbers for the records and write the records on groomed transaction blocks to the table based on the column values, wherein the table is sharded across nodes handling transactional operations in a multi-master distributed data management system to increase processing handling of the transactional operations.
 17. The apparatus of claim 16, wherein the write further comprises: receiving a next input group of records from scanning the table; generating unique commit timestamps; appending columns of the records to an in-memory buffer; and generating the tuple sequence numbers for the records written to the groomed transaction blocks, wherein upon a determination that there is no additional input group of records and the in-memory buffer is not full, flushing the in-memory buffer to at least one of a shared file system, an object store or a local cache.
 18. The apparatus of claim 17, wherein the processor configured to execute the instructions to: if a further input group of records is not available, notifying a distributed coordinator of a groom end point information; moving a log head beyond the groom end point; and pruning the log until no read processes remain.
 19. The apparatus of claim 18, wherein: the transactional operations comprise update, delete and insert operations; upon a successful transaction commit, the transaction-local side-log is appended to a log stream; a grooming process only reads the log and avoids uncommitted transaction changes; a thread performing the grooming process maintains a cursor on the log as an indication of a previous grooming cycle; in the log stream prior to a location that the cursor points to is marked for deletion; a pruning process deletes a portion of the log stream upon a determination that no ongoing read operation is in the portion log stream; and both the grooming process and read operations follow the previous grooming cycle such that read operations of data are monotonic.
 20. The apparatus of claim 19, wherein: the grooming process only reads log streams with commit timestamps less than a start time of the grooming process such that a grooming cycle has a bounded execution time; updated records are flagged with an end timestamp after the grooming process by a periodic background process such that the updated records are ignored by reading processes that need latest data or by reading processes that read data from a specific time period; the multi-master distributed data management system operates on two tiers of storage comprising: a first storage tier that is local to a node, and a second storage tier including a distributed shared file system or an object store; the first storage tier maintains a persistent version of logs to be used during recovery by the grooming process to start grooming from where the grooming process left off in a previous cycle, and caches frequently accessed portions of the second storage tier to enable fast access to data; and the second storage tier maintains the data stream and makes the data stream available to all of nodes in the multi-master distributed data management system. 